Power burner application to fin tube heat exchanger

ABSTRACT

A power burner, fin tube heat exchanger includes a plurality of parallel fin tubes connected at each end with a manifold to define a combustion chamber or enclosure. A gas and air mixture is provided to the enclosure by a blower and ignited. A flue gas collector enshrouds the fin tube enclosure and provides an exhaust path for the combusted flue products.

United States Patent 1191 Daugirda et al. v

1451 July 16, 1974 POWER BURNER APPLICATION TO FIN TUBEHEAT EXCHANGER Inventors: Paul G. Daugirda, Chicago; Leslie D. Smith, Hickory Hills, both of Ill.

Assignee: Rheem International, Inc., New

York, N .Y.

Filed: Feb. 14, 1973 Appl. No.: 332,368

US. Cl 126/392, 122/235 R, 431/328, 239/533 Int. Cl F24h l/34,

Field of Search 126/392; 122/262, 235 R; 431/328, 157; 239/533, 567

References Cited UNITED STATES PATENTS Parker 239/533 Vaughn 431/328 3,187,798 6/1965 Pokorny 431/328 x 3,302,705 2/1967 Whitten, Jr. 122/235 R x 3,315,646 4/1967 Witten,'.|r. 122/235 3,650,248 3/1972 M11161 122/235 R 3,704,748 12/1972 Hapgood 122/367 PF x Primary Examiner-William F. ODea Assistant Examiner-William C. Anderson Attorney, Agent, or Firm-Molinare, Allegretti, Newitt & Witcoff [5 7] ABSTRACT A power burner, fin tube heat exchanger includes a 1 plurality of parallel fin tubes connected at each end with a manifold to define a combustion chamber or enclosure. A gas and air mixture is provided to the enclosure by a blower and ignited. A flue gas collector enshrouds the fin tube enclosure and provides an exhaust path for the combusted flue products.

4 Claims, 4 Drawing Figures PATENTEDJUL I s M 3. 823.704

SHEET 1 0F 2 TERMINAL BLOCK ROOM THERMOSTAT 0 HIGH LIMIT CONTROL 78 I o o H5 v. W0 R0 6 C Yo GAS 58 LINE VALVE TRANSFORMER I TR I RELAY V TH C CHASlS (5 O O O O v5 v3 24v 24v 6 s CIRCULATOR fiDsI CONTROL O START CAPACITOR 85 82 SENSOR LOWER IGNITOR MOTOR 54 68 PATENTED JUL 1 6 I974 SHEET 2 BF 2 POWER BURNER APPLICATION TO FIN TUBE HEAT EXCHANGER BACKGROUND OF THE INVENTION burner then pass along the sides of the water tank and ultimately through an exhaust stack. The water is circulated either by gravity flow or a pump.

Apparatus of this type have been utilized for many years and provide an inexpensive and reasonably efficient method for heating water. Nonetheless, it is desirable to provide an improved heater construction with quick recovery characteristics of smaller size and with higher efficiency than prior art water heaters or heat exchangers. Likewise, it is desirable to provide a heat exchanger which may be utilized for a multiplicity of functions.

SUMMARY OF THE INVENTION In a principal aspect, the present invention comprises an'improved fin tube heat exchanger which includes a power burner positioned for fuel ignition within an enclosure defined by a number of parallel fin tube elements. The fin tube elements are connected with manifolds at each end and thus surround the burner. The fin tubes are also enshrouded by a flue gas collector so that combustion products may flow about the fin tubes to be discharged through a flue.

It is thus an object of the present invention to provide a heat exchanger which operates to combust a mixture of fuel and air at superatmospheric pressures.

It is a further object of the present invention to provide a power burner positioned within an enclosure defined by heat exchange elements. 1

Still another object of the present invention is to provide a power burner which has a greater efficiency than prior art heat exchangers.

A further object of the present invention is to provide a power burner heat exchanger construction which does not require any source of secondary air to effect complete combustion of the fuel.

Another object of the present invention is to provide a power burner heat exchanger having a burner with a low, even flame profile which avoids creating uneven heat within the combustion cavity of the exchanger.

One further object of the present invention is to provide a power burner, heat exchanger wherein the water or fluid being heated substantially surrounds the combustion region of the burner.

These and other objects, advantages and features of the present invention will be set forth in greater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWING Figures:

FIG. 1 is a perspective view of the improved power burner, heat exchanger of the present invention;

FIG. 2 is an exploded perspective view of the heat exchanger of the present invention;

FIG. 3 is a schematic wiring diagram illustrating the control circuit for the improved power burner, heat exchanger of the present invention; and

FIG. 4 is a side elevation of the burner element for the heat exchanger of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the apparatus of the present invention is depicted as including a plurality of substantially identical fin tubes 10 which are arranged parallel to one another and spaced substantially equidistant from a centerline axis 12. The fin tubes 10 are hollow for carrying water or the material which is to be heated. The tubes 10 include many external fins to improve heat transfer'to the fluid within the tubes. Such tubes 10 are known to persons skilled in the art of heat exchangers.

The fin tubes 10 extend through appropriate spaced openings 14 and 16 defined in header plates 18 and 20 respectively positioned at opposite ends of the tubes 10. Gaskets or seals 22 and 24 respectively are positioned against the plates 18 and 20. An inlet-outlet header 26 engages seal 22 against plate 18 to define one end manifold of the heat exchanger. A return header 28 engages gasket 24 against plate 20 to define the opposite end manifold of the heat exchanger. The plate 20, gasket 24 and header 28 include central passages 30, 32 and 34 respectively which will be discussed in more detail below.

The inlet-outlet header 26 includes a fluid inlet 36 for fluid admission and a fluid outlet 38 for fluid discharge from the fin tubes 10. Thus, in the embodiment disclosed, water, for example, will flow into the inlet 36, thence through tubes 10a mounted in openings 14a. Fluid then flows via the return header 28 into tubes 10!) mounted in openings 14b to be redirected via a header section 36b of header 36 through tubes 10c mounted in openings, 14c tothe manifold defined by return header 28, seal 24 and plate 20. The fluid is then again redirected through two of the remaining fin tubes 10, The fluid thus passes back and forth between the separate manifolds until it ultimately passes through the outlet 38.

The fin tube and manifold arrangement of the disclosed embodiment permit the fluid to flow in a parallel path through fin tubes six separate times or passes between the inlet 36 and outlet 38. Of course, the manifold and tube arrangement may be changed as required to provide any number of fluid passes.

The above-described fin tubes 10 and manifolds constitute the combustion chamber portion of the heat exchanger. A stainless steel mantel type burner 40 extends through the openings 34, 32 and 30 into the comdetail in FIG. 4. As shown in FIG. 4, the cone 42 inv .40 by a slight amountto permit the flow of a combustible gas mixture through perforations 39 in the burner 40.

Referring again to FIGS. 1 and 2, the burner 40'and cone 42 are positioned within the enclosure defined by the fin tubes as previously described. A combined blower housing and mixing chamber 48 is attached by fastening means 50 to the header 28. A flange 51 of housing 48 engages a peripheral flange 49 of burner 40 to hold the burner 40 rigidly in position within the combustion chamber.

Mounted within the housing 48 is a fan 52 driven by a motor 54. A-motor mounting plate 56 is positioned intermediate the fan 52 and motor 54 and is attached to the housing 48. The motor 54 is thus fixed to plate 56 with a shaft 57 connected to fan 52 to drive the fan 52.

A gas valve 58 is connected via a tube 60 to a gas inlet 62 of the housing 48. Thus, when the'valve 58 is in the open' position and the fan 52 is being operated, a mixture of gas and air is provided through the blower housing 48 to the burner 40. The gas valve 58 draws gas from a regulator set at a negative pressure to prevent gas from entering the housing and mixing chamber 48 v in the event the blower 52 malfunctions.

An igniter 64 is threaded through an appropriate opening 66 in the header 28. The igniter 64 provides a spark which ignites the combustible gas-air mixture within the enclosure defined by the fin tubes 10 and manifolds. A sensor 68 extends through another opening 70 in the header 28. The sensor 68 detects a temperature increase due to flame from the burner 40 and operates to turn off the igniter 64. g

The fin tubes 10 are surrounded by a flue gas collector or shroud 72. Baffles 74 may be attached to the interior of the shroud 72 to direct the flue gases into desired contact with the fin tubes 10. The shroud 72 includes a flue gas outlet 76 for discharge of combustion products from the interior of the shroud 72.

The operation of the power burner, fintube heat exchanger can be understood by reference to FIG. 3, a

circuit diagram for the apparatus. If the apparatus is' used to provide hot water for a hot water heating system in a home, initiation of operation of the mechanism is dependent upon closing of a control circuit in a room thermostat 78. When the circuit through the thermostat 78 is closed, a 24 volt circuit through a control panel 86 is energized. This causes the gas valve 58 to be opened and simultaneously turns on the electric spark igniter 64. in addition, a relay 80 energizing a 120 voltcircuit is operated. This causes the blower motor 54 to commence operation as well as a circulator 82 which is a mechanism for circulating fluid through the fin tubes 10.

The blower 52 then draws gas from the gas valve 58 and mixes it with air as' shown in FIG. 1 within the housing 48. The regulator associated with the gas valve 58 is preferably set at a negative pressure to prevent gas from entering the chamber 48 in the event the blower 52 malfunctions. The air-gas mixture provided by the blower 52 and gas valve 58 is a proper stoichiometric mix which will provide complete combustion. Thus, there is no necessity for a secondary air source within the enclosure defined by the fin tubes 10 and shroud 72.

The blower 52 forces the air-gas mixture into the burner 40 over the distribution cone 42. The particular shape of the cone 42 and burner 40 create a uniformly distributed flame on the surface of the burner 40. That is, elimination of the cone 42 will result in hot spots on the burner 40 and less efficient burning, thus lowering the efficiency of the apparatus and reducing the life of the parts. Also, with the burner construction as utilized in the present invention, the height of flames is short, thus preventing flame impingement on the fin tubes 10. This results in a longer life for the fin tubes 10 and also provides for more complete combustion.

When flame is detected by the sensor 68, the spark from the igniter 64 is terminated. The unit then opertime by sensor 68.

The combustion products pass radially outward from the burner 40 through the spaces between the fin tubes 10 and are circulated within the shroud 72. With this configuration, the entire combustion chamber is surrounded by water. That is, the fin tubes 10 and the manifolds all include circulating water. Heat provided by the combustion at the burner 40 is transported by radiation convection and conduction to the water surrounding the burner 40 and provides for increased efficiency of heat transfer. The result of this is lower heat loss than with a conventional heat exchanger for the same length and number of fin tubes. Also, insulation requirements are lower and no opening is required for secondary air to complete combustion.-

Thus, the heat transfer efficiency in a power burner configuration of the type disclosed as compared with a prior art atmospheric burner is approximately two times greater. This is due to a number of factors as discussed above. For example, the fin tubes surround the burner. The burner is constructed so that a low even flame pattern is provided. The fuel and air mixture is actually blown or injected into the combustion cavity and cause to circulate about in that cavity between the fin tubes at superatmospheric pressures.

Since the fin tube is preferably a serrated steel fin tube which causes a high resistance to thepassage of flue gases between the fins, pressure created by an atmospheric burner would not be sufficient to overcome this resistance and would thus lead to low efficiency. With a power burner, this difficulty is overcome and the flue gases are forced between the closely spaced fins on the fin tubes. Also, because no secondary air is required for combustion in a power burner, the burner can be completely surrounded by water backed surfaces creating a so-called pressurized combustion chamber. This pressure chamber wherein the water surrounds the actual area of combustion eliminates the need for bulky insulation and provides a heat exchanger package which is much smaller than the prior art atmospheric type heat exchangers. Therefore, it is possible to provide smaller sized heat exchangers having an output identical with larger atmospheric heat exchangers. For example, a 250,000 BTU per hour heat exchanger operating at atmospheric pressure requires more than five times the combustion area of similarly rated power burners.

Thus, it is to be understood that the described invention is to be limited only by the following claims and their equivalents.

1. An improved fin tube heat exchanger having a power burner comprising, in combination:

a plurality of parallel fin tubes defining a cylindrical combustion enclosure, each tube having a first end and a second end;

first and second manifolds connected respectively with said first and second tube ends, one of said manifolds including a center opening to the interior of the combustion enclosure;

a flue gas shroud enclosing said fin tubes and including a flue gas outlet;

power burner means positioned through said center opening to a position within said enclosure defined by said fin tubes, said burner including a perforated cylindrical mantel extending into said enclosure with one end of said mantel being open to receive a combustible fuel and air mixture, said mantel being spaced from said tubes for combustion within the region defined between the mantel and tubes, said burner also including a distribution member positioned within said mantel to distribute said mixture for ignition, said. member being cone shaped with a wide end and a narrow end, said member extending the length of the mantel with the narrow end adjacent the open end of the mantel, said wide end being separated slightly from the mantel to permit exit of the mixture from perforations at the end of the mantel, the narrow end of the member being rounded to effect distribution of the mixture, said burner also including a distribution member positioned within said mantel to distribute said mixture for ignition;

means for mixing a combustible fuel and air mixture;

blower means connecting said mixing means with said burner means for introducing said combustible mixture to said burner means; and

means for igniting said mixture at said burner.

2. The apparatus of claim 1 wherein said fin tubes and said manifold comprise a continuous fluid flow path including said inlet and outlet and wherein at least two parallel tube runs define said path.

3. The apparatus of claim 1 including means for controlling said burner.

4. The apparatus of claim 1 wherein the radius of the rounded end of the cone shaped member is about onethird the diameter of the mantel.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE 0F CORRECTION PATENT NO. 3,823,704

DATED July 16, 1974 |NVENTOR(5) 1 PAUL G. DAUGIRDA and LESLIE SMITH It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, lines 10-12, delete said burner also including a distribution member positioned within said mantel to distribute said mixture for ignition".

Signed and Scaled this T warty-seventh D a) 0 f June 1978 [SEAL] Attest:

R C. M ASON DONALD W. BANNER Attesting Ojficer Commissioner of Patents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 8Z3 704 Dated July 16 1974 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The assigneee should read Rheem Manufacturing Company Signed and sealed this 12th day of November 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR.

C. MARSHALL DANN Attesting Officer Commissioner of Patents F ORM PC4050 (10-69) UGCOMM-DC 60376-P69 U 5. GOVERNMENT PRIIIY NG OFFICE: 

1. An improved fin tube heat exchanger having a power burner comprising, in combination: a plurality of parallel fin tubes defining a cylindrical combustion enclosure, each tube having a first end and a second end; first and second manifolds connected respectively with said first and second tube ends, one of said manifolds including a center opening to the interior of the combustion enclosure; a flue gas shroud enclosing said fin tubes and including a flue gas outlet; power burner means positioned through said center opening to a position within said enclosure defined by said fin tubes, said burner including a perforated cylindrical mantel extending into said enclosure with one end of said mantel being open to receive a combustible fuel and air mixture, said mantel being spaced from said tubes for combustion within the region defined between the mantel and tubes, said burner also including a distribution member positioned within said mantel to distribute said mixture for ignition, said member being cone shaped with a wide end and a narrow end, said membEr extending the length of the mantel with the narrow end adjacent the open end of the mantel, said wide end being separated slightly from the mantel to permit exit of the mixture from perforations at the end of the mantel, the narrow end of the member being rounded to effect distribution of the mixture, said burner also including a distribution member positioned within said mantel to distribute said mixture for ignition; means for mixing a combustible fuel and air mixture; blower means connecting said mixing means with said burner means for introducing said combustible mixture to said burner means; and means for igniting said mixture at said burner.
 2. The apparatus of claim 1 wherein said fin tubes and said manifold comprise a continuous fluid flow path including said inlet and outlet and wherein at least two parallel tube runs define said path.
 3. The apparatus of claim 1 including means for controlling said burner.
 4. The apparatus of claim 1 wherein the radius of the rounded end of the cone shaped member is about one-third the diameter of the mantel. 